Heritability of defence and life-history traits in the two-spotted spider mite

Background: Two-spotted spider mites hide against predatory mites in a web of self-produced sticky silk. The proteins invested in this shelter may reduce investment in reproduction.
Questions: Do spider mite populations harbor genetic variation for web production, thereby enabling a response to selection by predation? Is adaptation affected by genetic trade-offs with life-history traits? The data were also used to test a central hypothesis in quantitative genetics, that heritability is indicative of the trait’s importance for fitness and is positively correlated with the amount of additive genetic variation across traits.
Method: Using a mother-daughter breeding design, the narrow-sense heritability and coefficients of additive genetic and residual variation (CVA and CVR) were determined for web production and six life-history traits. In addition, correlations between heritable traits were examined for genetic trade-offs.
Conclusions: Web production exhibited (marginally significant) heritability of 50% and a high CVA. Thus, web production is not a fixed defense-related trait but probably has the potential to evolve. Three life-history traits revealed heritable variation. Genetic trade-off with web production were not found, but could not be excluded either. Using the life-history data, a positive relationship was found between heritability and CVA, which supports the hypothesis that the relationship of traits with fitness influences their amount of heritable variation.